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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package com.nulldev.util.graphics.renderIt.ginterfaces.marlin.impl;

import java.lang.ref.Reference;

/**
 * This ReentrantContextProvider implementation uses a ThreadLocal to hold the
 * first ReentrantContext per thread and a ReentrantContextProviderCLQ to store
 * child ReentrantContext instances needed during recursion.
 *
 * Note: this implementation may keep up to one context in memory per thread.
 * Child contexts for recursive uses are stored in the queue using a WEAK
 * reference by default unless specified in the 2 argument constructor.
 *
 * @param <K> ReentrantContext subclass
 */
public abstract class ReentrantContextProviderTL<K extends ReentrantContext> extends ReentrantContextProvider<K> {
	// Thread-local storage:
	private final ThreadLocal<Reference<K>> ctxTL = new ThreadLocal<Reference<K>>();

	// ReentrantContext CLQ provider for child contexts:
	private final ReentrantContextProviderCLQ<K> ctxProviderCLQ;

	/**
	 * Create a new ReentrantContext provider using the given reference type among
	 * hard, soft or weak. It uses weak reference for the child contexts.
	 *
	 * @param refType reference type
	 */
	public ReentrantContextProviderTL(final int refType) {
		this(refType, REF_WEAK);
	}

	/**
	 * Create a new ReentrantContext provider using the given reference types among
	 * hard, soft or weak
	 *
	 * @param refTypeTL  reference type used by ThreadLocal
	 * @param refTypeCLQ reference type used by ReentrantContextProviderCLQ
	 */
	public ReentrantContextProviderTL(final int refTypeTL, final int refTypeCLQ) {
		super(refTypeTL);

		final ReentrantContextProviderTL<K> parent = this;

		this.ctxProviderCLQ = new ReentrantContextProviderCLQ<K>(refTypeCLQ) {
			@Override
			protected K newContext() {
				return parent.newContext();
			}
		};
	}

	/**
	 * Give a ReentrantContext instance for the current thread
	 *
	 * @return ReentrantContext instance
	 */
	@Override
	public final K acquire() {
		K ctx = null;
		final Reference<K> ref = ctxTL.get();
		if (ref != null) {
			ctx = ref.get();
		}
		if (ctx == null) {
			// create a new ReentrantContext if none is available
			ctx = newContext();
			// update thread local reference:
			ctxTL.set(getOrCreateReference(ctx));
		}
		// Check reentrance:
		if (ctx.usage == USAGE_TL_INACTIVE) {
			ctx.usage = USAGE_TL_IN_USE;
		} else {
			// get or create another ReentrantContext from CLQ provider:
			ctx = ctxProviderCLQ.acquire();
		}
		return ctx;
	}

	/**
	 * Restore the given ReentrantContext instance for reuse
	 *
	 * @param ctx ReentrantContext instance
	 */
	@Override
	public final void release(final K ctx) {
		if (ctx.usage == USAGE_TL_IN_USE) {
			ctx.usage = USAGE_TL_INACTIVE;
		} else {
			ctxProviderCLQ.release(ctx);
		}
	}
}
